Vertical Power Semiconductor Device and Manufacturing Method

ABSTRACT

A method of manufacturing a vertical power semiconductor device includes forming a drift region in a semiconductor body having a first main surface and a second main surface opposite to the first main surface along a vertical direction, the drift region including platinum atoms, and forming a field stop region in the semiconductor body between the drift region and the second main surface, the field stop region including a plurality of impurity peaks, wherein a first impurity peak of the plurality of impurity peaks is set a larger concentration than a second impurity peak of the plurality of impurity peaks, wherein the first impurity peak includes hydrogen and the second impurity peak includes helium.

TECHNICAL FIELD

The present disclosure is related to semiconductor devices, inparticular to vertical power semiconductor devices including a fieldstop region.

BACKGROUND

In semiconductor switching devices like IGBTs (insulated gate bipolartransistors) or diodes mobile charge carriers flood a low-doped driftregion and form a charge carrier plasma that provides a low on-stateresistance. One target of semiconductor device technology lies in thereduction of electric power dissipation in semiconductor switchingdevices. Although electric power dissipation may be improved by varyinga certain device parameter, this may lead to deterioration of anotherdevice characteristic. Thus, device parameters are designed duringtechnology development based on a number of tradeoffs to be met in viewof target device specifications.

There is a need to reduce electric power dissipation in vertical powersemiconductor devices.

SUMMARY

An example of the present disclosure relates to a vertical powersemiconductor device. The vertical power semiconductor device includes asemiconductor body having a first main surface and a second main surfaceopposite to the first main surface along a vertical direction. Thevertical power semiconductor device further includes a drift region inthe semiconductor body. The drift region includes platinum atoms (Pt). Afield stop region is arranged in the semiconductor body between thedrift region and the second main surface. The field stop region includesa plurality of impurity peaks. A first impurity peak of the plurality ofimpurity peaks has a larger concentration than a second impurity peak ofthe plurality of impurity peaks. The first impurity peak includeshydrogen (H) or is a hydrogen peak and the second impurity peak includeshelium (He) or is a helium peak.

Another example of the present disclosure relates to a method ofmanufacturing a vertical power semiconductor device. The method includesforming a drift region in a semiconductor body having a first mainsurface and a second main surface opposite to the first main surfacealong a vertical direction, wherein the drift region includes platinumatoms. The method further includes forming a field stop region in thesemiconductor body between the drift region and the second main surface,wherein the field stop region includes a plurality of impurity peaks,and a first impurity peak of the plurality of impurity peaks is set alarger concentration than a second impurity peak of the plurality ofimpurity peaks. The first impurity peak includes hydrogen or is ahydrogen peak and the second impurity peak includes helium or is ahelium peak.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description and onviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the embodiments and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments of avertical power semiconductor device and a method of manufacturing avertical power semiconductor device and together with the descriptionserve to explain principles of the embodiments. Further embodiments aredescribed in the following detailed description and the claims.

FIGS. 1 to 3 are schematic cross-sectional views for illustratingexamples of vertical power semiconductor devices including platinum in adrift region and hydrogen gettering provisions in a field stop region.

FIGS. 4 to 6 are schematic graphs illustrating exemplary impurityconcentrations c versus a vertical direction y in the field stop regionof vertical power semiconductor devices.

FIG. 7 is a schematic graph illustrating exemplary impurityconcentrations c versus a vertical direction y of a vertical powersemiconductor diode.

FIG. 8 is a schematic graph illustrating experimental leakage currentsIl versus a reverse or blocking voltage Vr of vertical powersemiconductor devices.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof and in which are shownby way of illustrations specific embodiments in which the invention maybe practiced. It is to be understood that other embodiments may beutilized and structural or logical changes may be made without departingfrom the scope of the present invention. For example, featuresillustrated or described for one embodiment can be used on or inconjunction with other embodiments to yield yet a further embodiment. Itis intended that the present invention includes such modifications andvariations. The examples are described using specific language, whichshould not be construed as limiting the scope of the appending claims.The drawings are not scaled and are for illustrative purposes only. Forclarity, the same elements have been designated by correspondingreferences in the different drawings if not stated otherwise.

The terms “having”, “containing”, “including”, “comprising” and the likeare open, and the terms indicate the presence of stated structures,elements or features but do not preclude the presence of additionalelements or features. The articles “a”, “an” and “the” are intended toinclude the plural as well as the singular, unless the context clearlyindicates otherwise.

The term “electrically connected” describes a permanent low-resistiveconnection between electrically connected elements, for example a directcontact between the concerned elements or a low-resistive connection viaa metal and/or heavily doped semiconductor material. The term“electrically coupled” includes that one or more intervening element(s)adapted for signal and/or power transmission may be connected betweenthe electrically coupled elements, for example, elements that arecontrollable to temporarily provide a low-resistive connection in afirst state and a high-resistive electric decoupling in a second state.An ohmic contact is a non-rectifying electrical junction with a linearor almost linear current-voltage characteristic.

Ranges given for physical dimensions include the boundary values. Forexample, a range for a parameter y from a to b reads as a≤y≤b. Aparameter y with a value of at least c reads as c≤y and a parameter ywith a value of at most d reads as y≤d.

The term “on” is not to be construed as meaning only “directly on”.Rather, if one element is positioned “on” another element (e.g., a layeris “on” another layer or “on” a substrate), a further component (e.g., afurther layer) may be positioned between the two elements (e.g., afurther layer may be positioned between a layer and a substrate if thelayer is “on” said substrate).

An example of a vertical power semiconductor device may include asemiconductor body having a first main surface and a second main surfaceopposite to the first main surface along a vertical direction. Thevertical power semiconductor device may further include a drift regionin the semiconductor body. The drift region may include platinum atoms.The vertical power semiconductor device may further include a field stopregion in the semiconductor body between the drift region and the secondmain surface. The field stop region may include a plurality of impuritypeaks. A first impurity peak of the plurality of impurity peaks has alarger concentration than a second impurity peak of the plurality ofimpurity peaks. The first impurity peak may include hydrogen or may be ahydrogen peak and the second impurity peak may include helium or may bea helium peak.

The vertical power semiconductor device may be a power semiconductordiode, or a power semiconductor IGBT (insulated gate bipolartransistor), or a reverse conducting (RC) IGBT or a power semiconductortransistor such as a power semiconductor IGFET (insulated gate fieldeffect transistor, e.g. a metal oxide semiconductor field effecttransistor). The vertical power semiconductor device may be configuredto conduct currents of more than 1 A or more than 10 A or even more than30 A and may be further configured to block voltages between loadterminals, e.g. between emitter and collector of an IGBT, or betweencathode and anode of a diode, or between drain and source of a MOSFET inthe range of several hundreds of up to several thousands of volts, e.g.400 V, 650V, 1.2 kV, 1.7 kV, 3.3 kV, 4.5 kV, 5.5 kV, 6 kV, 6.5 kV. Theblocking voltage may correspond to a voltage class specified in adatasheet of the power semiconductor device, for example.

The semiconductor body may include or consist of a semiconductormaterial from the group IV elemental semiconductors, IV-IV compoundsemiconductor material, III-V compound semiconductor material, or II-VIcompound semiconductor material. Examples of semiconductor materialsfrom the group IV elemental semiconductors include, inter alia, silicon(Si) and germanium (Ge). Examples of IV-IV compound semiconductormaterials include, inter alia, silicon carbide (SiC) and silicongermanium (SiGe). Examples of III-V compound semiconductor materialinclude, inter alia, gallium arsenide (GaAs), gallium nitride (GaN),gallium phosphide (GaP), indium phosphide (InP), indium gallium nitride(InGaN) and indium gallium arsenide (InGaAs). Examples of II-VI compoundsemiconductor materials include, inter alia, cadmium telluride (CdTe),mercury-cadmium-telluride (CdHgTe), and cadmium magnesium telluride(CdMgTe). For example, the semiconductor body may be a magneticCzochralski, MCZ, or a float zone (FZ) or an epitaxially depositedsilicon semiconductor body.

For example, an impurity concentration in the drift region may graduallyor in steps increase or decrease with increasing distance to the firstmain surface at least in portions of its vertical extension. Accordingto other examples the impurity concentration in the drift region may beapproximately uniform. For IGBTs based on silicon, a mean impurityconcentration in the drift region may be between 5×10¹² cm⁻³ and 1×10¹⁵cm⁻³, for example in a range from 1×10¹³ cm⁻³ to 2×10¹⁴ cm⁻³. In thecase of a semiconductor device based on SiC, a mean impurityconcentration in the drift region may be between 5×10¹⁴ cm⁻³ and 1×10¹⁷cm⁻³, for example in a range from 1×10¹⁵ cm⁻³ to 2×10¹⁶ cm⁻³. A verticalextension of the drift region may depend on voltage blockingrequirements, e.g. a specified voltage class, of the vertical powersemiconductor device. When operating the vertical power semiconductordevice in voltage blocking mode, a space charge region may verticallyextend partly or totally through the drift region depending on theblocking voltage applied to the vertical power semiconductor device.When operating the vertical power semiconductor device at or close tothe specified maximum blocking voltage, the space charge region mayreach or penetrate into the field stop region. The field stop region isconfigured to prevent the space charge region from further reaching tothe cathode or collector at the second main surface of the semiconductorbody. In this manner, the drift or base region may be formed usingdesired low doping levels and with a desired thickness while achievingsoft switching for the semiconductor device thus formed.

Since the field stop region aims at preventing the space charge regionfrom reaching the cathode or collector at the second main surface of thesemiconductor body in a voltage blocking mode at or around maximumspecified voltage blocking capabilities of the semiconductor device, amean net impurity concentration in the field stop layer may be higherthan in the drift region by at least one order of magnitude, forexample. Moreover, the mean net impurity concentration in the field stoplayer may be lower than the impurity concentration in a cathode contactlayer ore collector contact layer by at least one order of magnitude,for example.

For example, a total impurity concentration at a vertical position ofthe first impurity peak may predominantly include hydrogen, e.g. morethan 60% of hydrogen, or more than 70% of hydrogen, or more than 80% ofhydrogen, or even more than 90% of hydrogen. For example, a verticalimpurity concentration profile of the hydrogen may have a peak at avertical position of the first impurity peak, for example.

For example, a vertical impurity concentration profile of the helium mayhave a peak at a vertical position of the second peak, for example.

By combining the platinum in the drift region and the helium in thesecond impurity peak, a leakage current may be reduced by avoiding or atleast by reducing the undesired formation of platinum hydrogen complexesin the drift region. This may be achieved by gettering of hydrogen viathe second impurity peak including the helium. Thereby, undesireddiffusion of hydrogen from the first impurity peak into the drift regionmay be reduced or suppressed.

For example, a first vertical distance between the first impurity peakand the second impurity peak may range from 0 μm and ±5 μm, or from 2 μmto 5 μm, or from −2 μm to −5 μm. For example, the first impurity peakmay be arranged between the second impurity peak and the second mainsurface. According to another example, the first impurity peak may bearranged between the second impurity peak and the first main surface.The first and second impurity peaks may also coincide.

For example, a third impurity peak of the plurality of impurity peaksmay be disposed at a vertical distance from the second main surface thatdiffers from 0 to 300 nm and/or less than a half-width (HW) of thesecond impurity peak P2 from the second vertical distance of the secondimpurity peak. The third impurity peak may include hydrogen or may be ahydrogen peak. For example, a concentration of the third impurity peakmay be larger than a concentration of the second impurity peak.

For example, the second vertical distance may be larger than a thirdvertical distance between the second main surface and the first impuritypeak. Thus, a helium peak may be disposed between the drift region and ahydrogen peak of the field stop region, for example a hydrogen peakhaving a largest hydrogen peak concentration in the field stop region.This may allow for a beneficial gettering of hydrogen diffusing from thehydrogen peak toward the drift region, for example. Thereby, a leakagecurrent may be reduced by avoiding or at least reducing the undesiredformation of platinum-hydrogen complexes in the drift region.

For example, the second vertical distance may be smaller than a thirdvertical distance between the second main surface and the first impuritypeak. Decoration of vacancies caused by implantation of He may lead to abeneficial decrease of the lateral resistance in a surface area of thesecond main surface, for example.

For example, a fourth impurity peak of the plurality of impurity peaksmay include helium and may be disposed at a fourth vertical distancefrom the second main surface. The third vertical distance may rangebetween the second vertical distance and the fourth vertical distance.For example, a vertical impurity concentration profile of the helium maynot only have a peak at a vertical position of the second impurity peak,but may have another peak at a vertical position of the fourth impuritypeak. Along the vertical direction, a deepest hydrogen peak of the fieldstop region, i.e. a hydrogen peak of the field stop region having alargest vertical distance to the second main surface, e.g. the firstimpurity peak, may be arranged between opposite helium peaks, e.g. thesecond impurity peak and the fourth impurity peak, for example. Thereby,gettering of hydrogen diffusing from the hydrogen peak toward the driftregion may be further improved, for example. Furthermore, reducing thediffusion constant of hydrogen in the helium-containing peak regionlocated below the hydrogen-containing main peak may also contribute to areduced diffusion of hydrogen into the drift zone. A leakage current maythus be reduced by avoiding or at least reducing the undesired formationof platinum-hydrogen complexes in the drift region. For example, ahelium dose associated with the second impurity peak may also be spreadacross a plurality of second helium sub-peaks, e.g. by carrying out aplurality of helium ion implantations at different ion implantationenergies and/or different ion implantation angles, wherein the secondhelium sub-peaks may be arranged either between the first impurity peak,e.g. a hydrogen peak in the drift region, and the first main surface orbetween the first impurity peak and the second main surface. Likewise, ahelium dose associated with the fourth impurity peak may also be spreadacross a plurality of second helium sub-peaks, e.g. by carrying out aplurality of helium ion implantations at different ion implantationenergies and/or different ion implantation angles, wherein the fourthhelium sub-peaks may be arranged either between the first impurity peak,e.g. a hydrogen peak in the drift region, and the second main surface orbetween the first impurity peak and the first main surface. This maylead to approximately box-shaped helium concentration profiles along thevertical direction. By spreading the helium across a larger verticaldistance by multiple helium sub-peaks compared to a single helium peakimplantation, a certain helium dose or hydrogen gettering may beachieved at comparatively lower ion implantation damage compared to asingle ion implantation, for example.

For example, a ratio between a peak concentration of the first impuritypeak, e.g. a hydrogen peak concentration, and a peak concentration ofthe second impurity peak, e.g. a helium peak concentration, may rangefrom 10 to 1000, or may range from 50 to 500. Since helium ionimplantation doses are significantly smaller compared to protonimplantation doses with respect to generation of a certain concentrationof vacancies, the required total implantation dose for the differentpeaks for achieving a certain total integrated (into vertical directionalong the field stop profile) field stop doping dose can besignificantly reduced and therefore process time and process costs canbe reduced.

For example, a helium peak concentration of the second impurity peak,e.g. a helium concentration, may range from 1×10¹⁶ cm⁻³ to 2×10¹⁸ cm⁻³,or from 2×10¹⁶ cm⁻³ to 1×10¹⁸ cm⁻³, or from 5×10¹⁶ cm⁻³ to 5×10¹⁷ cm⁻³.

For example, a maximum concentration of platinum in the drift region mayrange from 5×10¹² cm⁻³ to 3×10¹⁴ cm⁻³. For example, a concentration ofplatinum may decrease from the second main surface toward and at leastpartly through the drift region. For example, a concentration ofplatinum may exhibit a minimum within the drift zone. For example,platinum may be introduced into the drift region by one or more ionimplantation processes into the front side or the backside of the waferand/or diffusion process(es) out of a diffusion source, e.g. a platinumsilicide on a surface of the semiconductor body.

For example, the drift region may have a vertical extension from thefield stop region to a pn-junction, e.g. a pn-junction between a driftregion and a body region of an IGBT or a pn-junction between the driftregion and an anode region of a diode. The pn-junction may be locatedcloser, e.g. at a smaller vertical distance, to the first main surfacethan to the second main surface. A maximum concentration of hydrogen inthe drift region may be smaller than 100%, or 50% or 20% of aconcentration of platinum along at least 50% of the vertical extensionof the drift region. The vertical extension of the drift region may beconfined by the pn-junction at a first end of the drift region orientedto the first main surface, and a second end of the drift region orientedto the second main surface, wherein the second end of the drift regionmay be at a transition between the drift region and the field stopregion. The hydrogen concentration in the drift region may be reduceddue to hydrogen gettering in the field stop region by the introductionof helium into the drift region, for example.

For example, the platinum atoms in the drift region may be configured asplatinum-hydrogen complexes and substitutional platinum. A maximumconcentration of the platinum-hydrogen complexes in the drift region maybe smaller than a concentration of the substitutional platinum along atleast 50% of the vertical extension of the drift region. For example,the maximum concentration of the platinum-hydrogen complexes in thedrift region may be at most 60% or even 40% or even 20% of theconcentration of the substitutional platinum along at least 50% of thevertical extension of the drift region. By keeping a concentration ofthe platinum-hydrogen complexes along a predominant part of the driftregion smaller than the concentration of the substitutional platinum, aleakage current, and thus electric power dissipation, of thesemiconductor device may be reduced.

Details described above with respect to the vertical semiconductor powerdevice, e.g. materials, dimensions, technical effects, likewise apply tothe examples of manufacturing methods described below.

An example of a method of manufacturing a vertical power semiconductordevice may include forming a drift region in a semiconductor body havinga first main surface and a second main surface opposite to the firstmain surface along a vertical direction, wherein the drift region mayinclude platinum. The method may further include forming a field stopregion in the semiconductor body between the drift region and the secondmain surface. The field stop region may include a plurality of impuritypeaks, and a first impurity peak of the plurality of impurity peaks isset a larger concentration than a second impurity peak of the pluralityof impurity peaks. The first impurity peak may include hydrogen or maybe a hydrogen peak and the second impurity peak may include helium ormay be a helium peak.

For example, forming the first impurity peak may include at least oneproton implantation process having a proton implantation dose rangingfrom 2×10¹³ cm⁻² to 5×10¹⁴ cm⁻². For example, a plurality of protonimplantation processes may be carried out, wherein a proton implantationdose may decrease with increasing proton implantation energy. Thus,hydrogen peak concentrations in the field stop region may decrease withan increase in a vertical distance from the second main surface, forexample.

For example, forming the second impurity peak may include at least onehelium ion implantation process. The semiconductor body may be annealedin a temperature range from 350° C. to 430° C. for 0.5 to 5 hours afterthe at least one proton implantation process and after the at least onehelium ion implantation process.

For example, a first vertical distance between the first impurity peakand the second impurity peak may be set in a range from 0 μm to ±5 μm.

For example, the method may further comprise forming a fourth impuritypeak in the field stop region by at least one helium ion implantationprocess. The fourth impurity peak may be set at a fourth verticaldistance from the second main surface. The first impurity peak may bearranged between the second impurity peak and the fourth impurity peakalong the vertical direction.

For example, the method may further comprise implanting helium ions intothe semiconductor body by a plurality of different ion implantation tiltangles. This may allow for setting a box-shaped vertical concentrationprofile of helium which may be a concentration profile having a largervertical extension, a smaller damage concentration and a lower peakconcentration than a single helium peak profile when assuming equalhelium implantation doses for both cases. Different ion implantationangles may be combined with different helium ion implantation energiesto achieve desired vertical concentration profiles of helium forimproving hydrogen gettering, for example.

For example, the platinum is introduced into the drift region at amaximum concentration ranging from 5×10¹² cm⁻³ to 3×10¹⁴ cm⁻³. Forexample, the platinum may be introduced by a diffusion process above750° C. or above 800° C. into the drift region. The platinum may beintroduced prior to the implantation of hydrogen, for example.

For example, the drift region has a vertical extension from the fieldstop region to a pn-junction. A maximum concentration of hydrogen in thedrift region may be set smaller than a concentration of platinum alongat least 50% of the vertical extension of the drift region.

For example, the platinum in the drift region may includeplatinum-hydrogen complexes and substitutional platinum. A maximumconcentration of the platinum-hydrogen complexes in the drift region maybe set smaller than a concentration of the substitutional platinum alongat least 50% of the vertical extension of the drift region.

For example, a maximum hydrogen concentration in the field stop regionmay be at least a factor of 5 larger, or a factor of 20 larger, or afactor 100 larger, or a factor of 500 larger than a maximum hydrogenconcentration in the drift region.

The examples and features described above and below may be combined.

In the following, further examples of vertical power semiconductordevices and manufacturing methods are explained in connection with theaccompanying drawings. Functional and structural details described withrespect to the examples above shall likewise apply to the exemplaryembodiments illustrated in the figures and described further below.

FIG. 1 is a schematic cross-sectional view illustrating an embodiment ofa vertical power semiconductor device 100. The vertical powersemiconductor device 100 includes a semiconductor body 102 having afirst main surface 104 and a second main surface 106 opposite to thefirst main surface 104. A thickness of the semiconductor body 102between the first main surface 104 and the second main surface 106ranges from several tens of micrometers to several hundreds ofmicrometers depending, inter alia, on a specified voltage class of thevertical power semiconductor device, for example.

Active device elements may be formed in an active device area of thesemiconductor body 102 at the first main surface 104. A portion wherethe active device elements are located is schematically indicated in thefigures by a dashed box 107. The active device area is an area of thesemiconductor body 102 where a load current flow enters/exits thesemiconductor body through the first main surface 104. In case of IGFETsor IGBTs, the active device area may include source regions electricallyconnected to a contact electrode through the first main surface 104. Asource to drain current or emitter to collector current may flow fromthe contact electrode through the first main surface 104 into the sourceregions. In case of diodes, the active device area may include anode orcathode regions electrically connected to the contact electrode throughthe first main surface 104. An anode to cathode current may flow fromthe contact electrode through the first main surface 104 into the anodeor cathode regions. Thus, the active device area may be restricted to afirst part of the first main surface through which load current flow isguided, for example.

The edge termination elements may be formed in an edge termination area,which is an area of the semiconductor body 102 that partly or fullysurrounds the active device area. Since pn junctions within thesemiconductor body 102, e.g. pn junctions between a body region and adrift region of an IGFET or an IGBT or pn junctions between a cathodeand an anode region of a diode, are not infinite, but terminate at theedge zones of the semiconductor body, this edge effect limits the devicebreakdown voltage below the ideal value that is set by the infiniteparallel plane junction. Care must be taken to ensure proper andefficient termination of the pn junction at the edge of thesemiconductor body. The edge termination area is a measure for ensuringproper and efficient termination of the pn junction. In the edgetermination area, the edge termination structures are formed forlowering the electric field at the edge of the semiconductor body.Depending on the voltage class of the semiconductor device, a lateraldimension of the edge termination area may vary. Semiconductor deviceswith higher voltage classes typically require larger lateral extensionsof their edge termination areas for ensuring proper termination of thepn junction. Examples of edge termination structures in the edgetermination area include field plates, junction termination extension(JTE) structures, variation of lateral doping (VLD) structures, forexample.

The vertical power semiconductor device 100 further includes a driftregion 108 in the semiconductor body 102. The drift region 108 includesplatinum. The platinum in the drift region 108 is schematicallyillustrated in the figures by crosses 109. A field stop region 110 isarranged in the semiconductor body 102 between the drift region 108 andthe second main surface 106. The field stop region 110 includes aplurality of impurity peaks. In the example illustrated in FIG. 1 ,three impurity peaks are illustrated. A first impurity peak P1 of theplurality of impurity peaks has a larger concentration c than a secondimpurity peak P2 of the plurality of impurity peaks. The first impuritypeak P1 is a hydrogen peak and the second impurity peak P2 is a heliumpeak. A first vertical distance d1 between the first impurity peak P1and the second impurity peak P2 ranges from 0 μm to ±5 μm. In theillustrated example, the first vertical distance d1 is negative. Hence,the second impurity peak P2 is arranged between the first impurity peakP1 and the first main surface 104. A second vertical distance d2 fromthe second main surface 106 to the second impurity peak P2 is thuslarger than a third vertical distance d3 from the second main surface106 to the first impurity peak P1.

The vertical power semiconductor device 100 further includes a thirdimpurity peak P3, e.g. a hydrogen peak that is disposed close to orcongruent with the second impurity peak P2. For example, the thirdimpurity peak P3 may be disposed at a vertical distance from the secondmain surface 106 that differs from 0 to ±300 nm with respect to thesecond vertical distance d2 of the second impurity peak P2. The thirdimpurity peak P3 is a hydrogen peak.

FIG. 2 is a schematic cross-sectional view for illustrating anotherembodiment of a vertical power semiconductor device 100. In theillustrated example, the first distance d1 is positive. Hence, thesecond impurity peak P2 is arranged between the first impurity peak P1and the second main surface 106. The second vertical distance d2 fromthe second main surface 106 to the second impurity peak P2 is thussmaller than the third vertical distance d3 from the second main surface106 to the first impurity peak P1.

FIG. 3 is a schematic cross-sectional view illustrating anotherembodiment of a vertical power semiconductor device 100. In theillustrated example, the vertical power semiconductor device 100 furtherincludes a fourth impurity peak P4 that is disposed at a fourth verticaldistance d4 from the second main surface 106. The fourth impurity peakP4 is a helium peak. The third vertical distance d3 ranges between thesecond vertical distance d2 and the fourth vertical distance d4. Thus,the first impurity peak P1 is arranged between the second and fourthimpurity peaks P2, P4. The vertical power semiconductor device 100further includes a fifth impurity peak P5, e.g. a hydrogen peak that isdisposed close to or congruent with the fourth impurity peak P4. Forexample, the fifth impurity peak P5 may be disposed at a verticaldistance from the second main surface 106 that differs from 0 to ±300 nmwith respect to the fourth vertical distance d4 of the fourth impuritypeak P4. The fifth impurity peak P5 is a hydrogen peak.

The schematic graphs of FIGS. 4 to 6 illustrate examples of hydrogen andhelium concentration profiles along the vertical direction y in thefield stop region 108 of the vertical power semiconductor device 100.For the sake of clarity, the third and fifth impurity peaks P3, P5 asillustrated in FIGS. 1 to 3 are omitted in FIGS. 4 to 6 although thesepeaks may also be present.

Referring to the schematic graph illustrated in FIG. 4 , helium ions areimplanted into the semiconductor body 102 by a plurality of differention implantation tilt angles. A vertical profile of a heliumconcentration c2 is a superposition of profiles of single verticalhelium concentrations c21, c22, c23, wherein the profiles of singlevertical helium concentrations c21, c22, c23 are formed by helium ionimplantations at constant energy but different ion implantation angles.The helium peak P2 is arranged between the hydrogen peak P1 and thefirst main surface.

Referring to the schematic graph illustrated in FIG. 5 , in addition tohelium ions implanted into the semiconductor body 102 as described withreference to FIG. 5 , further helium ions are implanted into thesemiconductor body 102 by even larger tilt angles than the onesassociated with the helium peak P2 but equal ion implantation energy. Asa result, a helium peak P4 is formed that is arranged between thehydrogen peak P1 and the second main surface. A vertical profile of ahelium concentration c4 is a superposition of single profiles ofvertical helium concentrations c41, c42, wherein the single profiles ofvertical helium concentrations c41, c42 are formed by helium ionimplantation at constant energy but different ion implantation angles.

Referring to the schematic graph illustrated in FIG. 6 , helium ions areimplanted into the semiconductor body 102 by a plurality of differention implantation tilt angles. A vertical profile of a heliumconcentration c4 is a superposition of profiles of single verticalhelium concentrations c41, c42, c43, c44, c45, c46, wherein the profilesof single vertical helium concentrations c41, c42, c43, c44, c45, c46are formed by helium ion implantations at constant energy but differention implantation angles. The helium peak P4 is arranged between thehydrogen peak P1 and the second main surface.

Referring to the schematic graph illustrated in FIG. 7 , exemplaryvertical profiles of concentrations c of impurities are illustratedalong the vertical direction y from the second main surface, e.g. acathode side of a diode, toward the first main surface, e.g. an anodeside of a diode. The vertical profiles are divided into a cathode region112, the field stop region 110 and the drift region 108.

A vertical profile of a helium concentration cHe is similar to theexample illustrated in FIG. 1 . A vertical profile of a hydrogenconcentration cH has a main peak P1 in the field stop region 110arranged between a peak P2 of the helium concentration cH and the firstmain surface.

A vertical profile of a vacancy concentration cV includes peaks atpositions close to or equal to the first and second peaks P1, P2.

A vertical profile of n-type doping concentration cD includes peaks atpositions close to or equal to the first and second peaks P1, P2, whichare due to formation of hydrogen-related donors. The vertical profile ofn-type doping concentration cD increases toward a maximum at or close tothe second main surface in the collector or cathode region 112. Themaximum may be configured as a cathode contact region, for example.

In the illustrated schematic example, a vertical profile of Ptconcentration cPt decreases from the second main surface toward thedrift region 108 and is larger in the drift region than the hydrogenconcentration cH. Lowering of the hydrogen concentration cH in the driftregion 108, and thus reduction of undesired platinum-hydrogen complexesin the drift region can be achieved by gettering of hydrogen around thehelium peak P2.

The above examples allow for a reduction of electric power dissipationin semiconductor devices by lowering leakage current in the drift region108 of the semiconductor device. FIG. 8 is a schematic graphillustrating experimental results of an electric leakage current Il forreverse or blocking voltages Vr. A leakage current Il1 is associatedwith a semiconductor device sample as described in the examples above,i.e. a semiconductor device sample including a helium peak in the fieldstop region for gettering of hydrogen and reducing undesiredplatinum-hydrogen complexes in the drift region. A leakage current Il2is associated with a semiconductor device sample lacking the provisionsas described with reference to the sample of Il1. A difference inleakage current ΔIl allows for quantification of the reduction of therelation between the concentration of platinum/hydrogen complexes andsubstitutional platinum and thus of leakage current-induced electricpower dissipation, for example.

The aspects and features mentioned and described together with one ormore of the previously described examples and figures, may as well becombined with one or more of the other examples in order to replace alike feature of the other example or in order to additionally introducethe feature to the other example.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A method of manufacturing a vertical powersemiconductor device, the method comprising: forming a drift region in asemiconductor body having a first main surface and a second main surfaceopposite to the first main surface along a vertical direction, the driftregion including platinum atoms; and forming a field stop region in thesemiconductor body between the drift region and the second main surface,the field stop region including a plurality of impurity peaks, wherein afirst impurity peak of the plurality of impurity peaks is set a largerconcentration than a second impurity peak of the plurality of impuritypeaks, wherein the first impurity peak includes hydrogen and the secondimpurity peak includes helium.
 2. The method of claim 1, wherein formingthe first impurity peak includes at least one proton implantationprocess having a proton implantation dose ranging from 2×10¹³ cm⁻² to5×10¹⁴ cm⁻².
 3. The method of claim 2, wherein forming the secondimpurity peak includes at least one helium ion implantation process, andwherein the semiconductor body is annealed in a temperature range from350° C. to 430° C. for 0.5 to 5 hours after the least one protonimplantation process and after the at least one helium ion implantationprocess.
 4. The method of claim 1, wherein a first vertical distancebetween the first impurity peak and the second impurity peak is set in arange from 0 μm to ±5 μm.
 5. The method of claim 1, further comprising:forming a fourth impurity peak in the field stop region by at least onehelium ion implantation process, wherein the fourth impurity peak is setat a fourth vertical distance from the second main surface, and whereinthe first impurity peak is arranged between the second impurity peak andthe fourth impurity peak along the vertical direction.
 6. The method ofclaim 1, further comprising: implanting helium ions into thesemiconductor body by a plurality of different ion implantation tiltangles.
 7. The method of claim 14, wherein the platinum is introducedinto the drift region at a maximum concentration ranging from 5×10¹²cm⁻³ to 3×10¹⁴ cm⁻³.
 8. The method of claim 1, wherein the drift regionhas a vertical extension from the field stop region to a pn-junction,and wherein a maximum concentration of hydrogen in the drift region isset smaller than a concentration of platinum along at least 50% of thevertical extension of the drift region.
 9. The method of claim 1,wherein the platinum in the drift region includes platinum-hydrogencomplexes and substitutional platinum, and wherein a maximumconcentration of the platinum-hydrogen complexes in the drift region isset smaller than a concentration of the substitutional platinum along atleast 50% of a vertical extension of the drift region.
 10. The method ofclaim 1, wherein a maximum hydrogen concentration in the field stopregion is at least a factor of 5 larger than a maximum hydrogenconcentration in the drift region.
 11. The method of claim 1, wherein athird impurity peak of the plurality of impurity peaks is disposed at athird vertical distance from the second main surface that differs from 0to 300 nm from a second vertical distance of the second impurity peakwith respect to the second main surface, wherein the second verticaldistance is larger than the third vertical distance between the secondmain surface and the first impurity peak, and wherein the third impuritypeak includes hydrogen.
 12. The method of claim 11, wherein the secondvertical distance is larger than the third vertical distance between thesecond main surface and the first impurity peak.
 13. The method of claim11, wherein the second vertical distance is smaller than the thirdvertical distance between the second main surface and the first impuritypeak.
 14. The method of claim 11, wherein a concentration of the thirdimpurity peak is larger than a concentration of the second impuritypeak.
 15. The method of claim 11, wherein a fourth impurity peak of theplurality of impurity peaks includes helium and is disposed at a fourthvertical distance from the second main surface, and wherein the thirdvertical distance ranges between the second vertical distance and thefourth vertical distance.
 16. The method of claim 1, wherein a ratiobetween a peak concentration of the first impurity peak and a peakconcentration of the second impurity peak ranges from 10 to
 1000. 17.The method of claim 1, wherein a helium peak concentration of the secondimpurity peak ranges from 1×10¹⁶ cm⁻³ to 2×10¹⁸ cm⁻³.
 18. The method ofclaim 1, wherein a maximum concentration of platinum in the drift regionranges from 5×10¹² cm⁻³ to 3×10¹⁴ cm⁻³.